Frank L. Soucie (left) posted on the Facebook Timeline of his son Frank Soucie.Handout

A 27-year-old Queens man walked into a police station last night and dramatically announced he had murdered his mother’s boyfriend — hours after that man’s body was found buried in a newly dug grave in his own backyard, cops said.

The suspect, Derek Tudor, who was accompanied by his father, burst into tears when he told detectives he had suffocated 60-year-old retired mailman Frank Soucie on April 21, police said.

Earlier in the day Tudor had been spotted by a neighbor tossing out a burned sleeping bag outside the second-floor apartment where he lived with his mom Stephanie Verni and Soucie at 1866 Putnam Ave in Ridgewood. The neighbor’s call to cops led to the discovery of the grave containing Soucie’s body.

Murder charges are now pending against Tudor, according to NYPD spokesman Paul Browne.

“This is very gruesome,” said their neighbor Debbie Webster. “When he disappeared last week, we all knew something terrible had happened.”

“There was animosity between Frank and the kid,” Webster noted. “Sometimes they would argue and he would yell at [Soucie], ‘I’ll kill you!’ but never did we think it would escalate into something like this.”

“Frank was a very docile man,” she said. “He wouldn’t hurt a fly. He didn’t deserve to die this way. We’re all, as neighbors, elated [Tudor] was apprehended.”

Another neighbor, Emma Alameda, called Tudor “a real weirdo.”

“The last two days he was walking around with a hood over his head, hiding his face,” Alameda said.

After Soucie was reported missing last week, cops conducted an extensive search for him, checking his usual haunts, including casinos, a bird sanctuary and a house trailer he has in West Virginia, without any success, police said.

Yesterday,Tudor startled a upstairs neighbor when he ran into their third-floor apartment.

“My girlfriend said she was in the bathroom when she felt someone staring at her,” said Raymond Velez, 44, who lives in that upstairs apartment. “He [Tudor] was inside our apartment and she asked, ‘What are you doing here?’ “

“He said he was locked out of the apartment and he went up the fire escape, I’m assuming up to the roof,” Velez recalled. “Then he went back downstairs and asked [the mother of Velez’s girlfriend] for the key to get back in. He was acting strange.”

“Then he dumped a laundry bag in the thrash outside. I looked inside because I thought why is he throwing that out.”

“There were three black garbage bags one inside the other and inside was a burnt sleeping bag,” Velez said. “We found it weird because we knew he was into camping. Why would [Tudor] throw that out like that?”

“He looked scared and when he came downstairs he just ran off. He looked nervous,” Velez said.

After cops were called to the scene, they found the sleeping bag, and then went to the roof.

There, detectives found a large plastic storage bin that had blood both inside and outside of it, as well as ammonia, according to Police Department spokesman Browne.

When the detectives looked down from the roof, they saw a fresh mound of soil in the shape of a human body in a garden in the backyard, Browne said.

After the mound was dug up, police found Soucie’s body wrapped in cloth, Browne said.

Tudor showed up at the 102nd Precinct in Queens hours later, at 6 p.m., accompanied by his dad, Anthony Tudor, Browne said.

When Derek Tudor told a cop there he was there to turn himself in, the officer asked him what crime he had committed, Browne said.

“Murder,” Tudor replied, according to Browne.

Detectives from the 104th Precinct then were called — because Soucie lived in the confines of that precinct — and spoke to Tudor.

Tudor told them he had suffocated Soucie on April 21, and then began crying, according to Browne.

He then refused to say anything else, invoking his right to a lawyer, Browne said.